The world energy crisis has greatly stimulated a demand for solid fuel products, both natural and artifical. This invention relates generally to a method of producing a solid fuel element, and more specifically to a method of producing fireplace logs having a relatively large amount of coal. The logs have a relatively small amount of paraffin and a surface impregnated with a solution of paraffin and detergent. The invention is also directed to the logs so produced.
In the past, synthetic fireplace logs have been introduced into the market place. Many synthetic fireplace logs in the prior art have been made from material such as paper, sawdust, woodchip or shavings and waste vegetable fibers combined with some forms of adhesive binders. For example, U.S. Pat. No. 4,179,269 discloses a fireplace log and a method of producing the log by using ground coal, wood fibers and slack wax. However, many of these logs require large amounts of energy to manufacture and contain large amounts of paraffin and other wax-like substances. High wax content logs are generally volatile and are not recommended for any tupe of freestanding fireplace application. In addition, the BTU output of the prior art synthetic fireplace logs is relatively low and the burning time considerably less as compared with synthetic logs made in accordance with the invention. Furthermore, the manufacturing processes of the prior art have produced synthetic fireplace logs that are extruded from compacting compression equipment. Such procedures require relatively expensive compression equipment to produce the required high pressures on the order of 55,000 pounds per square inch. Logs made from such equipment produce, when ignited, undesirable airborne products which produce a fire hazard. The heating efficiency of such fireplace logs is undesirably low.
Therefore, an objective of the invention is to overcome the above and other disadvantages of the prior art by the provision of a greatly improved solid fuel product, particularly suitable for use as a solid igniter for fireplace logs and also capable of a wide utility in the solid fuel field.
According to the present invention, a coal log is produced having superior form but is less expensive than prior art logs in that only a small percentage of solid paraffin is required. The log is produced by a simple method that requires relatively low compression. In addition, the outer surface of the log may be coated with a paraffin or a solution of paraffin and a surfactant. It is also advantageous to incorporate the surfactant into the body of the solid fuel element. According to the method of the present invention, a major portion of pulverized coal and a minor portion of paraffin wax, in solid form, are mixed so that a heterogeneous extrudeable mixture is formed. Surfactant soluble in paraffin may be present or added at this stage. The mixture is compressed. The compressed form may then be passed through a liquid wax mix consisting of paraffin or paraffin and surfactant.
According to the present invention, a fireplace log is produced consisting essentially of about 80-95% by weight of pulverized coal and approximately 5-20% by weight of paraffin wax.
It is an object of the present invention to provide a simple, inexpensive and efficient method for the manufacture of a solid fuel element.
Another object of the invention is to provide a new and improved method for manufacture of a solid fuel element with efficient operations and at a low energy cost.
A further object of the invention is to provide an inexpensive fuel element having suitable characteristics for use as a fireplace log.
A still further object of the invention is to provide a safe solid fuel alternative with improved heat values.
Yet another object of the invention is to provide a coating for a coal fuel element which is easily ignitable and which renders the product clean to handle. The coating contains paraffin and a minor portion of surfactant or detergent.
These and other objects of the invention will become clear in reference to the detailed description of the invention.